Southern Cross University law lecturer Aiden Rickets liaises between protesters and police.

He says it appears the officer has gone too far.

"Clearly where a person's got both of their arms locked and they cant remove themselves, to spray them in the face with capsicum, you know, isn't just assault, it pretty much amounts to torture," he said.

"We would view that very very gravely and we would certainly expect that the senior police would investigate that and take appropriate action."

Police guidelines state capsicum spray can only be used under three circumstances: To protect human life; As a less lethal option for controlling people where violent resistance or confrontation occurs; Or as protection against animals.

The Lock the Gate alliance, which organised the protest, says it will be lodging a complaint against the police.

New South Wales Police have confirmed an internal investigation into the incident is underway.